arm64: dts: qcom: sc7280: rename edp_out label to mdss_edp_out

Rename the edp_out label in the sc7280 platform to mdss_edp_out
so that the nodes related to mdss are all grouped together in
the board specific files.

Signed-off-by: Sankeerth Billakanti <quic_sbillaka@quicinc.com>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Stephen Boyd <swboyd@chromium.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Link: https://lore.kernel.org/r/1647452154-16361-2-git-send-email-quic_sbillaka@quicinc.com